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Thread: Exhaust upgrade mps gen 1

  1. #21

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    Quote Originally Posted by premhk View Post
    I had one of those was $650 year ago. Sold it now..
    @premhk what do you have now?

  2. #22

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    i made more power with the stock DP but deleted CAT and put a 2 inch straight through muffler

  3. #23

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    Smart!

  4. #24

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    yeah is, plus you save about 2 grand lol for same gain. Just remember you need back pressure. 3 inch systems sound good, give ok numbers/gains, but dont hold enough back pressure.

  5. #25
    Join Date
    Jan 2009
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    Wahroonga
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    36
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    903

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    Quote Originally Posted by premhk View Post
    yeah is, plus you save about 2 grand lol for same gain. Just remember you need back pressure. 3 inch systems sound good, give ok numbers/gains, but dont hold enough back pressure.
    Backpressure? On a Turbo? Do tell... I think you'll find that to be incorrect. NA engines, yes. Forced Induction, no.

  6. #26

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    You sure about that??? Then throw a 5 inch exhaust on your car..... lol

    Here:
    "VOLUMETRIC EFFICIENCY AND BACKPRESSURE
    Although the turbine recovers wasted exhaust gas energy from the expansion of the hot exhaust gas, the kinetic energy of the flowing exhaust gas and the acoustic energy of the exhaust gas, the working turbine also causes an increase in exhaust gas backpressure. This increase in backpressure can reduce the engine's volumetric efficiency. A typical, streetable turbo system has more exhaust backpressure than boost pressure and the power gains from such systems are due to the increase in the density of the intake charger, not due to increases in volumetric efficiency. (Volumetric efficiency, if you don't remember, is the volume of intake charge inhaled during the intake stroke vs. the actual displacement of the cylinder. VE is expressed as a percentage; the larger the VE, the better.) Backpressure is higher than boost pressure because the smaller turbine housings and turbine wheels used to ensure a quick spool-up time also, by nature, restrict the exhaust flow. We will explain the mechanics of this in more detail a little later. Racing turbos, the latest generation of medium-sized turbos and turbochargers for engines where throttle response is not much of an issue (like fixed industrial engines, long haul trucks and aircraft), have free-flowing turbines that have less exhaust pressure than intake pressure. Engines using these turbos often do have improved volumetric efficiency. This condition, where boost is higher than backpressure, is called crossover and crossover is what ever turbo system designer strives for. In crossover, VE percentages as high as 110 percent are not unheard of. Unfortunately, some of the design features that can create a free-flowing turbo can also contribute to turbo lag, something that is not desirable in a street-driven car that needs a wide dynamic power band.
    Excessive backpressure is hard to manage in a boosted four-stroke engine. Excess backpressure causes what is known as reversion. Reversion is when hot exhaust gas gets pumped backwards into the engine during the overlap period. Reversion can cause the engines internals to get excessively hot as cross flow of the cool intake charge during overlap is one of the ways an engine cools its self internally. Hot internal parts can trigger uncontrolled combustion and engine-destroying detonation. Because of this, it is sometimes not a good idea to really crank the boost on an engine that has a small, high-backpressure turbo - in other words, the kind of turbo that usually comes on a factory turbo car.
    This is a good reason not to go crazy with a boost controller on a factory-equipped turbo car. A little more boost, perhaps 4 to 5 psi might be tolerated, but trying for 20psi could be flirting with disaster. On small turbo cars with a lot of backpressure, camshaft overlap should be kept to a minimum. This means that the stock cam usually will work best. To deal with the problems associated with backpressure and reversion, the engine's tuning must also be compromised with richer mixtures and more retarded timing than what would normally be optimal for the best power. Even on full race turbocharged cars with low backpressure turbos, camshaft overlap should be several degrees less with more lobe separation angle than on an equivalent naturally aspirated engine, unless physical measurements indicate that the engine is in crossover in the engine's operational range.
    Because of backpressure and VE issues, the correct turbo size for the application is very important when designing a turbo system. A small, quick-spooling turbo can be restrictive, causing a great deal of backpressure and reducing VE at higher rpm. This means that small turbos should be limited to lower boost levels. A big, free-flowing turbo can be laggy and unresponsive, making it unpleasant for street driving but producing awesome power at higher rpm. To combat high backpressure and possible reversion, the compromised tuning needed to prevent destruction with an overboosted small turbo will also reduce power. If a small turbocharger is running backpressure to boost ratio of more than about 1.8:1, a supercharger has a good chance of performing better. Fortunately, it is easy to design a reasonable responsive, powerful turbo system with a ratio of less than this.
    In future installments, we will delve deeper into turbo tech, discuss some more advantages and disadvantages of turbo vs. superchargers and give some guidelines and parameters so you can figure out what it takes to build a system that meets your needs. "
    Last edited by PremHK; 03-09-2012 at 07:19 PM.

  7. #27
    Join Date
    Apr 2010
    Location
    Canberra
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    9,459

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    all i gained from that wall of text is you contradicting yourself
    you said you gained more power by keeping one stock cat...
    but that article says that by removing cats, fitting larger free-flowing exhaust, yes, you create more lag, but you gain more power...
    some people are willing to have more lag for that extra power up top

  8. #28

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    hence i left the other cats there sam. Otherwise i would have ripped em all out.

  9. Default

    sorry for the noob question, but why would anyone want 200+ (or massive loads of power) atw when you only have fwd? how does all that power translate to speed? and whats the point of having hp and no torque? you save shifting time when there is minimal lag becasue it get you outa the corner quicker. - atleast this is what i thought.

  10. #30
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    Apr 2010
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    Canberra
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    Default Re: Exhaust upgrade mps gen 1

    Quote Originally Posted by dar_vedar View Post
    sorry for the noob question, but why would anyone want 200+ (or massive loads of power) atw when you only have fwd? how does all that power translate to speed? and whats the point of having hp and no torque? you save shifting time when there is minimal lag becasue it get you outa the corner quicker. - atleast this is what i thought.
    I currently hold ~220kw atw from 4500-6500rpm, and because of nature of bigger turbo, torque steer is reduced...

    And can tell you right now, in 3rd and 4th it translates to a heap more speed
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
    3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings

  11. #31

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    So at 120+ speeds its a monster!!! Where can you get away with that in Sydney nowadays Sam lmao!!!???

  12. #32
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    Default Re: Exhaust upgrade mps gen 1

    Quote Originally Posted by premhk View Post
    So at 120+ speeds its a monster!!! Where can you get away with that in Sydney nowadays Sam lmao!!!???
    Get perfectly usable power from ~50kph in 3rd...

  13. #33

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    ur car is good for targa tasmania now.....lol

  14. #34

    Default Exhaust upgrade mps gen 1

    *tsk* *tsk*


    Peter "SLIXX"

  15. #35

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    when u getting ur exhaust pete?!

  16. #36

    Default Exhaust upgrade mps gen 1

    Quote Originally Posted by premhk View Post
    when u getting ur exhaust pete?!
    Waiting for @2XS to quote on parts
    Then hopefully book it in next month


    Peter "SLIXX"

    Snapped by Tangcla - FB Page
    Currently RaydTuned
    Lots of love from 2XS Racing & Dan's Garage Detailing

  17. #37
    Join Date
    Jun 2009
    Location
    Newcastle
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    1,413

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    When testing exhaust systems on turbo engines so makers will give a spec for maximum allowable vacume in system after the turbo, anything above the maximum vacum indicates a problem.

    Just felt like saying that, dont care if anyone cares


    Quote Originally Posted by SarcasticOne View Post
    all i gained from that wall of text is you contradicting yourself
    you said you gained more power by keeping one stock cat...
    but that article says that by removing cats, fitting larger free-flowing exhaust, yes, you create more lag, but you gain more power...
    some people are willing to have more lag for that extra power up top
    Every man should have a V8 ute.....with a Chev badge.....and a Southern Cross sticker! Mods? What mods?

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